docs: def _assign_zones(self):
          """Assign all RainCloudyFaucetZone managed by faucet."""
          for zone_id in range(1, 5):
              zone = \
                  RainCloudyFaucetZone(
                      parent=self._parent,
                      controller=self._controller,
                      faucet=self,
                      zone_id=zone_id)
  
              if zone not in self.zones:
                  self.zones.append(zone)